A woman named Yukari married a busy man with a recluse step-son named Hiro. One day, she catches him masturbating and can't hide her arousal or excitement. Feeling lonely despite being happy with her husband, she decides to help Hiro overcome his issues with girls by teaching him about female bodies. As they grow closer during these intimate lessons, Yukari finds herself enjoying their interactions more than expected. Eventually, they become so close that Hiro initiates sexual contact while they are embracing each other. Despite feeling guilty at first due to her relationship with her husband, Yukari gives in to her desires and begins having passionate sex with Hiro. Their taboo relationship continues as they explore each other's bodies every chance they get, eventually leading them to cross boundaries between parent and child in their forbidden incestuous love affair...

再婚した夫は多忙で、義理の息子は引きこもり…愛する人と結ばれて、幸せながらも寂しさ抱える「ゆかり」は、義息子ヒロ君のオナニーを目撃する。若くてギンギンに勃起したチ○コに動揺と興奮を隠しきれない「ゆかり」は、一人トイレにこもり自慰行為で自分をなぐさめるのだった。義息子が引きこもるのは‘女の子に嫌われた’のが原因だったことを知った「ゆかり」は、女性へのトラウマ克服のため女の身体を手取り足取り教え込むことにした。夫とSEXレスだった「ゆかり」は、ぎこちなく身体に触れてくる義息子を微笑ましく思い、やがて前のめりにがっついて来る様子に女の顔を見せるのだった。生挿入で合体し、がむしゃらに腰を振る義息子の若くて硬いチ○コがたまらなく気持ちいい「ゆかり」は、覚えたてのSEXに無我夢中のヒロ君に求められて女を取り戻していく。「父さんと俺、どっちが気持ちいいの？」「ヒロ君のチ○ポがいい～！」夫への背徳感に突き動かされ、来る日も来る日も互いの身体を貪るように愛し合う母子は、禁断の近親相姦で親子の垣根を越えてしまったのだった…